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Within geoelectrical imaging, the choice of measurement configurations and electrode locations is known to control the image resolution. Previous work has shown that optimized survey designs can provide a model resolution that is superior to standard survey designs. This paper demonstrates a methodology to optimize resolution within a target area, while limiting the number of required electrodes, thereby selecting optimal electrode locations. This is achieved by extending previous work on the 'Compare-R' algorithm, which by calculating updates to the resolution matrix optimizes the model resolution in a target area. Here, an additional weighting factor is introduced that allows to preferentially adding measurement configurations that can be acquired on a given set of electrodes. The performance of the optimization is tested on two synthetic examples and verified with a laboratory study. The effect of the weighting factor is investigated using an acquisition layout comprising a single line of electrodes. The results show that an increasing weight decreases the area of improved resolution, but leads to a smaller number of electrode positions. Imaging results superior to a standard survey design were achieved using 56 per cent fewer electrodes. The performance was also tested on a 3-D acquisition grid, where superior resolution within a target at the base of an embankment was achieved using 22 per cent fewer electrodes than a comparable standard survey. The effect of the underlying resistivity distribution on the performance of the optimization was investigated and it was shown that even strong resistivity contrasts only have minor impact. The synthetic results were verified in a laboratory tank experiment, where notable image improvements were achieved. This work shows that optimized surveys can be designed that have a resolution superior to standard survey designs, while requiring significantly fewer electrodes. This methodology thereby provides a means for improving the efficiency of geoelectrical imaging.

Electrical resistivity tomography (ERT) is increasingly being used to investigate unstable slopes and monitor the hydrogeological processes within. But movement of electrodes or incorrect placement of electrodes with respect to an assumed model can introduce significant resistivity artefacts into the reconstruction. In this work, we demonstrate a joint resistivity and electrode movement reconstruction algorithm within an iterative Gauss-Newton framework. We apply this to ERT monitoring data from an active slow-moving landslide in the UK. Results show fewer resistivity artefacts and suggest that electrode movement and resistivity can be reconstructed at the same time under certain conditions. A new 2.5-D formulation for the electrode position Jacobian is developed and is shown to give accurate numerical solutions when compared to the adjoint method on 3-D models. On large finite element meshes, the calculation time of the newly developed approach was also proven to be orders of magnitude faster than the 3-D adjoint method and addressed modelling errors in the 2-D perturbation and adjoint electrode position Jacobian.

Measurement errors can play a pivotal role in geophysical inversion. Most inverse models require users to prescribe or assume a statistical model of data errors before inversion. Wrongly prescribed errors can lead to over- or under-fitting of data; however, the derivation of models of data errors is often neglected. With the heightening interest in uncertainty estimation within hydrogeophysics, better characterisation and treatment of measurement errors is needed to provide improved image appraisal. Here we focus on the role of measurement errors in electrical resistivity tomography (ERT). We have analysed two time-lapse ERT datasets: one contains 96 sets of direct and reciprocal data collected from a surface ERT line within a 24 h timeframe; the other is a two-year-long cross-borehole survey at a UK nuclear site with 246 sets of over 50,000 measurements. Our study includes the characterisation of the spatial and temporal behaviour of measurement errors using autocorrelation and correlation coefficient analysis. We find that, in addition to well-known proportionality effects, ERT measurements can also be sensitive to the combination of electrodes used, i.e. errors may not be uncorrelated as often assumed. Based on these findings, we develop a new error model that allows grouping based on electrode number in addition to fitting a linear model to transfer resistance. The new model explains the observed measurement errors better and shows superior inversion results and uncertainty estimates in synthetic examples. It is robust, because it groups errors together based on the electrodes used to make the measurements. The new model can be readily applied to the diagonal data weighting matrix widely used in common inversion methods, as well as to the data covariance matrix in a Bayesian inversion framework. We demonstrate its application using extensive ERT monitoring datasets from the two aforementioned sites.

A full-scale field experiment applying 4D (3D time-lapse) cross-borehole Electrical Resistivity Tomography (ERT) to the monitoring of simulated subsurface leakage was undertaken at a legacy nuclear waste silo at the Sellafield Site, UK. The experiment constituted the first application of geoelectrical monitoring in support of decommissioning work at a UK nuclear licensed site. Images of resistivity changes occurring since a baseline date prior to the simulated leaks revealed likely preferential pathways of silo liquor simulant flow in the vadose zone and upper groundwater system. Geophysical evidence was found to be compatible with historic contamination detected in permeable facies in sediment cores retrieved from the ERT boreholes. Results indicate that laterally discontinuous till units forming localized hydraulic barriers substantially affect flow patterns and contaminant transport in the shallow subsurface at Sellafield. We conclude that only geophysical imaging of the kind presented here has the potential to provide the detailed spatial and temporal information at the (sub-)meter scale needed to reduce the uncertainty in models of subsurface processes at nuclear sites.

Hypertensive disorders affect approximately 8–10% of all pregnancies and include pre-eclampsia, gestational hypertension and pre-existing chronic hypertension, which may be primary or secondary. New onset hypertension in pregnancy is defined as a sustained systolic blood pressure (sBP) ≥140 mmHg and/or diastolic blood pressure (dBP) ≥90 mmHg, and severe hypertension diagnosed when sBP ≥160 mmHg and/or dBP ≥110 mmHg. Gestational hypertension and pre-eclampsia are most common, affecting 4.2–7.9% and 1.5–7.7% respectively. Chronic hypertension affects 0.6–2.7% of pregnancies but may be under-reported due to early physiological adaptations in pregnancy lowering blood pressure or unknown preconception blood pressure. New onset hypertension developing at any stage of pregnancy requires a full history, examination, and investigations to delineate an underlying cause, assess for target organ damage and the presence of pre-eclampsia to assign risk. Developing a hypertensive disorder in pregnancy is associated with increased life-long cardiometabolic risk and other cardiovascular risk factors should be minimised to improve a woman's long-term health. [ABSTRACT FROM AUTHOR]

Fibromuscular dysplasia is the most common cause of renovascular hypertension in young adults under 40 years old. It is potentially amenable to renal artery angioplasty, which frequently normalizes blood pressure. However, limited options exist if angioplasty is not technically possible, or restenosis occurs. Here, we describe 2 patients who presented with hypertension secondary to renal artery stenosis. In the first case, a young adult with hypertension secondary to renal artery stenosis (fibromuscular dysplasia), developed restenosis 11 weeks after an initially successful renal artery angioplasty. In the second case, a patient with neurofibromatosis type 1 was diagnosed with hypertension secondary to renal artery stenosis. Angioplasty was not possible due to multiple branch occlusions. Both individuals went on to have successful renal autotransplantations, which ultimately cured their hypertension. In this article, we review the background, indications, and blood pressure outcomes in relation to renal autotransplantation in nonatherosclerotic renal artery stenosis. [ABSTRACT FROM AUTHOR]

This paper describes the Late Pleistocene to Holocene stratigraphy of the River Lambourn; a minor headwater of the River Thames in the Berkshire Downs. The Quaternary valley-fill comprises around 5-8. m of Late Pleistocene gravels overlain by Holocene peats and chalky clays. Quaternary deposits overlie an irregular rockhead erosion surface with deep scouring particularly evident on prominent bends in the valley. The gravels subdivide into a lower unit of chalky gravels overlain by coarse flint gravels. Ground penetrating radar suggests that gravels at depth are relatively structureless, but at the top show well-developed point-bar accretion surfaces which occur in association with peat-filled sinuous channels. These probably date from around the Pleistocene-Holocene boundary and may have formed in response to climate change and increased groundwater outflow as stream hydrology changed from the short-duration, high-magnitude flows of the Lower Dryas to the uniform, low-magnitude flows of the Holocene. Holocene peats initially infilled abandoned floodplain channels at around 10. kyr BP but later encroached over much of the Lambourn floodplain. A progressive upward decrease in organic material and an increase in the proportion of chalky clays from around 4. kyr BP probably occurred in response to floodplain accretion coupled with increased erosion of the chalk catchment related to agricultural clearance and a wetter climate.

Measurement sensors permanently installed on landslides will inevitably change their position over time due to mass movements. To interpret and correct the recorded data, these movements have to be determined. This is especially important in the case of geoelectrical monitoring, where incorrect sensor positions produce strong artefacts in the resulting resistivity models. They may obscure real changes, which could indicate triggering mechanisms for landslide failure or reactivation. In this paper we introduce a methodology to interpolate movements from a small set of sparsely distributed reference points to a larger set of electrode locations. Within this methodology we compare three interpolation techniques, i.e., a piecewise planar, bi-linear spline, and a kriging based interpolation scheme. The performance of these techniques is tested on a synthetic and a real-data example, showing a recovery rate of true movements to about 1% and 10% of the electrode spacing, respectively. The significance for applying the proposed methodology is demonstrated by inverse modelling of 4D electrical resistivity tomography data, where it is shown that by correcting for sensor movements corresponding artefacts can virtually be removed and true resistivity changes be imaged.

Interpersonal relationships are the recent focus of research identifying protective factors in adolescent psychological health. Using an attachment theory perspective, this study examines the relationship of normative attachment strength and individual differences in attachment expectancies on self-reports of depression and stress in 511 Australian high school students. Attachment reorganisation was demonstrated, but only father attachment uniquely predicted self-reported stress. Age moderated the relationships between peers and depression and stress among romantically involved adolescents. Individual differences in attachment styles, particularly anxious attachment, were most predictive of adolescent psychological health. These findings highlight the complexity of adolescent attachment relationships and suggest that interventions target both normative and individual factors in adolescent development to enhance adolescent psychological health.

BACKGROUND: Arterial stiffness, as measured by arterial pulse wave velocity (PWV), is an established biomarker for cardiovascular risk and target-organ damage in individuals with hypertension. With the emergence of new devices for assessing PWV, it has become evident that some of these devices yield results that display significant discrepancies compared with previous devices. This discrepancy underscores the importance of comprehensive validation procedures and the need for international recommendations. METHODS: A stepwise approach utilizing the modified Delphi technique, with the involvement of key scientific societies dedicated to arterial stiffness research worldwide, was adopted to formulate, through a multidisciplinary vision, a shared approach to the validation of noninvasive arterial PWV measurement devices. RESULTS: A set of recommendations has been developed, which aim to provide guidance to clinicians, researchers, and device manufacturers regarding the validation of new PWV measurement devices. The intention behind these recommendations is to ensure that the validation process can be conducted in a rigorous and consistent manner and to promote standardization and harmonization among PWV devices, thereby facilitating their widespread adoption in clinical practice. CONCLUSIONS: It is hoped that these recommendations will encourage both users and developers of PWV measurement devices to critically evaluate and validate their technologies, ultimately leading to improved consistency and comparability of results. This, in turn, will enhance the clinical utility of PWV as a valuable tool for assessing arterial stiffness and informing cardiovascular risk stratification and management in individuals with hypertension. [ABSTRACT FROM AUTHOR]

Background and purposeA number of therapies in development for patients with central nervous system injury aim to reduce disability by improving function of surviving brain elements rather than by salvaging tissue. The current study tested the hypothesis that, after adjusting for a number of clinical assessments, a measure of brain function at baseline would improve prediction of behavioral gains after treatment.MethodsTwenty-four patients with chronic stroke underwent baseline clinical and functional MRI assessments, received 6 weeks of rehabilitation therapy with or without investigational motor cortex stimulation, and then had repeat assessments. Thirteen baseline clinical/radiological measures were evaluated for ability to predict subsequent trial-related gains.ResultsAcross all patients, bivariate analyses found that greater trial-related functional gains were predicted by (1) smaller infarct volume, (2) greater baseline clinical status, and (3) lower degree of activation in stroke-affected motor cortex on baseline functional MRI. When these 3 variables were further assessed using multivariate linear regression modeling, only lower motor cortex activation and greater clinical status at baseline remained significant predictors. Note that lower baseline motor cortex activation was also associated with larger increases in motor cortex activation after treatment.ConclusionsLower motor cortex activity at baseline predicted greater behavioral gains after therapy, even after controlling for a number of clinical assessments. The boosts in cortical activity that paralleled behavioral gains suggest that in some patients, low baseline cortical activity represents underuse of surviving cortical resources. A measure of brain function might be important for optimal clinical decision-making in the context of a restorative intervention.

Orthopedic reconstructive surgery can be physically demanding. The musculoskeletal related demands related to performing shoulder arthroplasty are unknown. This study investigates the prevalence of musculoskeletal injuries associated with performing shoulder arthroplasty. An anonymous online survey based on the validated Nordic Musculoskeletal Questionnaire (NMQ) was distributed to society members of the American Shoulder and Elbow Surgeons. The REDCap based branching chain logic survey consisted of four main sections including: 1) personal demographics, 2) practice demographics, 3) NMQ questionnaire, and 4) effects of injury. A novel addition to the nine-region NMQ survey evaluated these areas for bothersome subclinical symptoms with no formal treatment requirement. Overall, 71% of 87 responding surgeons reported musculoskeletal symptoms related to performing shoulder arthroplasty. Within this group, 72% reported primary subclinical pain and 9% reported secondary exacerbation of a previous injury. Symptomatic regions and diagnoses were most often wrist/hand discomfort (20.7%) due to carpal tunnel syndrome and basilar thumb arthritis. Other associated symptoms included spine discomfort due to degenerative disc disease in the cervical (9.4%) or lumbar (18.4%) regions and elbow pain (6.7%) due to lateral epicondylitis or posterior interosseus nerve entrapment. The most common factors related to symptoms were case volume (24%), patient beach-chair operative positioning (17%), and table height (17%). Twenty-five surgeons required time off for work-related symptoms: 23 required <1 week and two required >1 week. Nine surgeons pursued nonoperative treatment and four surgeons underwent surgical intervention. Among all factors assessed, private practice surgeons reported symptoms significantly less frequently than those at tertiary referral (academic) centers. A high percentage of orthopedic surgeon's experience musculoskeletal symptoms related to shoulder arthroplasty. The three most commons areas of work-related pain in shoulder arthroplasty are wrist/hand discomfort, degenerative changes in the cervical and lumbar areas, and elbow pain. [ABSTRACT FROM AUTHOR]